Relay system and relay device

ABSTRACT

A ring control unit controls the ring network by transmitting and receiving a control frame through ring ports, and receives an address table deletion command via the control frame. When a first deletion command is received, an address table processing unit prohibits a learning process to the address table and then starts deleting the address table. Then, when a N-th (N is an integer of 2 or more) deletion command is received in a period before the completion of the deletion of the address table, the address table processing unit continues to execute the deletion of the address table.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2014-183601 filed on Sep. 9, 2014, the content of which is herebyincorporated by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a relay system and a relay device, forexample, a relay system and a relay device using a ring protocolspecified by ITU-T (International Telecommunication UnionTelecommunication Standardization Sector) G.8032.

BACKGROUND OF THE INVENTION

For example, Japanese Patent Application Laid-Open Publication No.2013-519265 (Patent Document 1) describes a method for preventingrepetitive refreshing of an address table which occurs at a neighbornode in the recovery from a fault in a ring network using a ringprotocol specified by ITU-T G.8032. Specifically, in the recovery from afault, a neighbor node usually receives a fault switch-back frame (NR,RB) from an owner node and deletes information of blocked port retainedby both ring ports. According to the method of the Patent Document 1,however, the neighbor node does not delete the information of blockedport but updates it with information of the blocked port contained inthe fault switch-back frame.

SUMMARY OF THE INVENTION

As described in the Patent Document 1, for example, the ring protocolspecified by ITU-T G.8032 has been known as one of ring protocols. Thisring protocol is sometimes referred to as ERP (Ethernet RingProtection). The ring protocol specifies that flushing (deletion) of anaddress table (FDB (Forwarding DataBase)) is executed in accordancewith, for example, a R-APS (SF) frame, R-APS (NR, RB) frame, and others.Although details will be described later, the R-APS (SF) frame functionsas a fault notification frame and the R-APS (NR, RB) frame functions asa fault switch-back frame.

Here, in the ring protocol, each relay device on the ring networksometimes receives fault notification frames resulting from the samefault several times in sequence. In such a case, the relay device has toexecute flushing of the address table (FDB) every time when receivingthe fault notification frame. Meanwhile, the time required for theflushing of the address table (FDB) is sufficiently longer than thereception interval of the fault notification frames in some cases. Inthis case, the flushing is restarted all over again while the flushingof the address table (FDB) is still being executed. As a result, aperiod required for substantially completing the flushing of the addresstable (FDB) becomes longer, which may lead to a problem that high-speedpath switching on the ring network becomes difficult.

The present invention has been made in view of the problem mentionedabove, and an object of the present invention is to realize high-speedpath switching on a ring network in a relay system and a relay deviceusing a ring protocol specified by ITU-T G.8032.

The above and other objects and novel characteristics of the presentinvention will be apparent from the description of the presentspecification and the accompanying drawings.

The following is a brief description of an outline of the typicalembodiment of the invention disclosed in the present application.

A relay system according to the present embodiment is provided with aplurality of relay devices constituting a ring network. At least one ofthe plurality of relay devices includes: a plurality of ports includinga first port and a second port; an address table; an address tableprocessing unit; and a ring control unit. The first port and the secondport are connected to the ring network. The address table retains acorrespondence relation among a MAC address, a VLAN identifier, and theplurality of ports. The address table processing unit performs a processto the address table. The ring control unit controls the ring network bytransmitting and receiving a control frame through the first port or thesecond port and receives a deletion command to delete the address tablevia the control frame. Here, when the first deletion command isreceived, the address table processing unit prohibits a learning processof the correspondence relation retained in the address table and thenstarts deleting the address table. Then, when the N-th (N is an integerof 2 or more) deletion command is received in a period before completionof the deletion of the address table, the address table processing unitcontinues to execute the deletion of the address table.

The effects obtained by typical embodiments of the invention disclosedin the present application will be briefly described below. That is, itis possible to realize high-speed path switching on a ring network in arelay system and a relay device using a ring protocol specified by ITU-TG.8032.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration example to bea premise of a relay system according to the first embodiment of thepresent invention;

FIG. 2 is a schematic diagram illustrating an example of a faultmonitoring method in the relay system of FIG. 1;

FIG. 3 is a diagram illustrating an example of an operation sequence atthe time of fault presence to be a premise of the relay system of FIG.1;

FIG. 4 is a diagram illustrating a frame transfer path after pathswitching of the ring network is performed by the operation of FIG. 3;

FIG. 5 is an explanatory diagram schematically illustrating an operationexample of the principle part of the relay device according to the firstembodiment of the present invention;

FIG. 6 is a block diagram illustrating a configuration example of therelay device of FIG. 5;

FIG. 7 is a schematic diagram illustrating a configuration example ofthe address table of FIG. 6;

FIG. 8 is an explanatory diagram schematically illustrating an operationexample around the ERP processing unit and the OAM processing unit inthe relay device of FIG. 6;

FIG. 9 is a flowchart illustrating an example of process contentsperformed by the FDB processing unit of FIGS. 6 and 8; and

FIG. 10 is a flowchart illustrating an example of the process contentsperformed by the ERP control unit of FIGS. 6 and 8 in a relay deviceaccording to the second embodiment of the present invention.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

In the embodiments described below, the invention will be described in aplurality of sections or embodiments when required as a matter ofconvenience. However, these sections or embodiments are not irrelevantto each other unless otherwise stated, and the one relates to the entireor a part of the other as a modification example, details, or asupplementary explanation thereof. Also, in the embodiments describedbelow, when referring to the number of elements (including number ofpieces, values, amount, range, and the like), the number of the elementsis not limited to a specific number unless otherwise stated or exceptthe case where the number is apparently limited to a specific number inprinciple, and the number larger or smaller than the specified number isalso applicable.

Further, in the embodiments described below, it goes without saying thatthe components (including element steps) are not always indispensableunless otherwise stated or except the case where the components areapparently indispensable in principle. Similarly, in the embodimentsdescribed below, when the shape of the components, positional relationthereof, and the like are mentioned, the substantially approximate andsimilar shapes and the like are included therein unless otherwise statedor except the case where it is conceivable that they are apparentlyexcluded in principle. The same goes for the numerical value and therange described above.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that componentshaving the same function are denoted by the same reference charactersthroughout the drawings for describing the embodiments, and therepetitive description thereof will be omitted.

First Embodiment General Configuration and General Operation of RelaySystem (Premise)

FIG. 1 is a schematic diagram illustrating a configuration example to bea premise of a relay system according to the first embodiment of thepresent invention. The relay system illustrated in FIG. 1 includes aplurality of (here, 5) relay devices SWa to SWe constituting a ringnetwork 10. Each of the relay devices SWa to SWe has two ring ports(first and second ports) Pr[1] and Pr[2] and m (m is an integer of 1 ormore) user ports Pu[1] to Pu[m]. Although the number of relay devicesconstituting the ring network 10 is assumed to be 5 in this example, thenumber is not limited to this, and may be 2 or more.

The ring network 10 is controlled based on, for example, a ring protocolspecified by ITU-T G 8032. In other words, each of the relay devices SWato SWe is provided with various control functions based on the ringprotocol. Each of the relay devices SWa to SWe is a L2 switch whichperforms relay process of a layer 2 (L2) of an OSI reference model ormay be a L3 switch which performs relay process of a layer 3 (L3).However, since the relay process on the ring network 10 is performedbased on the L2, the case where each of the relay devices SWa to SWe isthe L2 switch is taken as an example here.

The two ring ports Pr[1] and Pr[2] are each connected to the ringnetwork 10. In other words, each of the relay devices SWa to SWe isconnected via the ring ports Pr[1] and Pr[2] in a ring shape, so thatthe ring network 10 is formed. In the example of FIG. 1, the ring ports(first ports) Pr[1] of the relay devices SWa, SWb, SWc, SWd and SWe areconnected to the ring ports (second ports) Pr[2] of the neighboringrelay devices SWb, SWc, SWd, SWe and SWa via a communication line,respectively.

The user ports Pu[1] to Pu[m] are connected to predetermined usernetworks. In the example of FIG. 1, the user ports Pu[1] to Pu[m] of therelay devices SWa to SWe are connected to user networks 11 a to 11 e,respectively. In each of the user networks 11 a to 11 e, relay devices,various information processing devices (server device, terminal deviceand others) and others are arranged appropriately.

Here, based on ITU-T G.8032, the relay device SWa is set as an ownernode, and the relay device SWb is set as a neighbor node. A link betweenthe owner node and the neighbor node is referred to as RPL (RingProtection Link). When there is no fault on the ring network 10, therelay device SWa controls the ring port Pr[1] located at one end of theRPL to a block state BK, and the relay device SWb controls the ring portPr[2] located at the other end of RPL to the block state BK. The portcontrolled to the block state BK blocks frames from passing through it.

When there is no fault on the ring network 10, this RPL prevents thelooping of a communication path on the ring network 10. Morespecifically, as illustrated in FIG. 1, a communication path 12 via therelay devices SWe, SWd and SWc is formed between the relay device SWaand the relay device SWb. Frame transfer between the user networks 11 ato 11 e is performed on this communication path 12.

FIG. 2 is a schematic diagram illustrating an example of a faultmonitoring method in the relay system of FIG. 1. As illustrated in FIG.2, the relay devices SWa to SWe are provided with monitoring pointsMEPa1 to MEPe1 corresponding to the ring ports (first ports) Pr[1]respectively, and are provided with monitoring points MEPa2 to MEPe2corresponding to the ring ports (second ports) Pr[2] respectively.

Here, ITU-T G.8032 specifies that a CC (Continuity check) function ofEthernet (registered trademark) OAM is used for monitoring presence orabsence of fault in a link between the relay devices. Ethernet OAM hasbeen standardized by “ITU-T Y.1731” and “IEEE802.1ag”, etc. as astandard for monitoring the continuity between devices. In the CCfunction, a monitoring section is set by monitoring points referred toas MEP (Maintenance End Point) as illustrated in FIG. 2. MEPs at bothends of each monitoring section monitor the continuity of eachmonitoring section by transmitting and receiving a CCM (Continuity CheckMessage) frame which is a continuity monitoring frame at regularintervals.

In the example of FIG. 2, the monitoring point MEPa1 of the relay deviceSWa sets a CCM monitoring section 15 ab between itself and themonitoring point MEPb2 of another device (SWb), thereby monitoring thecontinuity between the first port Pr[1] of its own device and the secondport Pr[2] of the other device (SWb) connected thereto. Meanwhile, themonitoring point MEPb2 of the relay device SWb also sets the CCMmonitoring section 15 ab between itself and the monitoring point MEPa1of another device (SWa), thereby monitoring the continuity between thesecond port Pr[2] of its own device and the first port Pr[1] of theother device (SWa) connected thereto.

Similarly, CCM monitoring sections 15 bc, 15 cd, 15 de, and 15 ae aresequentially set on the ring network 10. In each CCM monitoring section(for example, 15 ab), when the monitoring point on one end (MEPa1) doesnot receive a CCM frame from the monitoring point on the other end(MEPb2) within a predetermined period, the monitoring point on one endrecognizes the continuity with respect to the monitoring point of theother end (MEPb2) as a LOC (Loss Of Continuity) state. The predeterminedperiod is, for example, 3.5 times as long as a transmission interval ofthe CCM frame (typically 3.3 ms).

In this case, the monitoring point of one end (MEPa1) transmits the CCMframe having a flag attached to a RDI (Remote Detect Indication) bitwhen transmitting the CCM frame to the monitoring point of the other end(MEPb2). The monitoring point of the other end (MEPb2) recognizes thecontinuity with respect to the monitoring point of one end (MEPa1) as aRDI state by receiving the CCM frame having a flag attached to the RDIbit from the monitoring point of one end (MEPa1). Each of the relaydevices SWa to SWe determines presence or absence of fault in the linkconnected to the ring ports Pr[1] and Pr[2] of its own device based onpresence or absence of recognition of a LOC state or a RDI state in themonitoring points (MEP) of its own device.

<<Operation of Relay System at the Time of Fault Presence (Premise)>>

FIG. 3 is a diagram illustrating an example of an operation sequence atthe time of fault presence to be a premise of the relay system ofFIG. 1. In FIG. 3, first, the ring port Pr[1] of the relay device SWaserving as an owner node and the ring port Pr[2] of the relay device SWbserving as a neighbor node are both controlled to a block state BK.

In this state, though not illustrated, the relay device SWa serving asthe owner node transmits R-APS (NR, RB) frames specified by ITU-T G.8032on the ring network 10 at regular intervals (for example, every 5 s).The R-APS frame is a kind of a control frame based on Ethernet OAM, andis recognized by information of an OpCode region in the frame or thelike. NR denotes absence of request (No Request) and RB denotes theblock of RPL (RPL Blocked).

Specifically, the R-APS (NR, RB) frame means that the ring network 10has no fault and the RPL (in other words, the ring port Pr[1] of therelay device SWa) is thus controlled to the block state BK. The R-APS(NR, RB) frame is transmitted also in the case of performing aswitch-back operation in the recovery from a fault in addition to thecase of no fault like this. When the switch-back operation is carriedout, the R-APS (NR, RB) frame functions as a fault switch-back frame.

In this case, the R-APS (NR, RB) frame contains information of a portcontrolled to the block state BK (the port is referred to as blockedport and the information is referred to as blocked port information inthis embodiment). Here, the blocked port information is {SWa} and{Pr[1]}. {SWa} represents a node identifier (ID) of the relay deviceSWa, and {Pr[1]} represents a port identifier (ID) of the ring portPR[1]. In this manner, in the present specification, {AA} is assumed torepresent an identifier of “AA”.

As illustrated in FIG. 3, each of the plurality of relay devices SWa toSWe is provided with blocked port information memory units 20[1] and20[2]. FIG. 3 illustrates the blocked port information memory units ofthe relay device SWc as a typical example of the blocked portinformation memory units of the plurality of relay devices SWa to SWe.When the relay device SWc receives blocked port information at the ringport Pr[1], the relay device SWc retains the blocked port information inthe blocked port information memory unit 20[1]. Also, when the relaydevice SWc receives blocked port information at the ring port Pr[2], therelay device SWc retains the blocked port information in the blockedport information memory unit 20[2]. In the example of FIG. 3, since therelay device SWc receives a R-APS (NR, RB) frame containing the blockedport information ({SWa} and {Pr[1]}) from the relay device SWa at thering port Pr[1], the relay device SWc retains the blocked portinformation in the blocked port information memory unit 20[1].

The case where a fault occurs on the link between the relay device SWdand the relay device SWe in the above-mentioned situation as indicatedby step S101 of FIG. 3 is assumed. In this case, as indicated by stepS102, the relay device SWd detects the fault (SF) on the link connectedto the ring port Pr[1] based on the monitoring result at the monitoringpoint MEPd1 illustrated in FIG. 2. SF is an abbreviation of signal fail.In response to this, the relay device SWd controls the ring port Pr[1]to the block state BK and flushes (deletes) an address table (FDB).

Similarly, as indicated by step S102, the relay device SWe also detectsthe fault (SF) on the link connected to the ring port Pr[2] based on themonitoring result at the monitoring point MEPe2 illustrated in FIG. 2.In response to this, the relay device SWe controls the ring port Pr[2]to the block state BK and flushes (deletes) an address table (FDB).

Subsequently, as indicated by step S103, the relay device SWd which hasdetected the fault (SF) transmits a first R-APS (SF) frame containingblocked port information ({SWd}, {Pr[1]}) on the ring network 10. TheR-APS (SF) frame functions as a fault notification frame. In the samemanner, the relay device SWe also transmits a first R-APS (SF) framecontaining blocked port information ({SWe}, {Pr[2]}) on the ring network10.

The R-APS (SF) frames transmitted by the relay devices SWd and SWe arerelayed by each relay device until the frames reach the ring port in theblock state BK. Here, as indicated by step S104, when receiving theR-APS (SF) frame from the relay device SWd, the relay device SWc flushesthe address table (FDB).

More specifically, in the relay device SWc, the blocked port information({SWd}, {Pr[1]}) contained in the R-APS (SF) frame from the relay deviceSWd is different from the blocked port information ({SWa}, {Pr[1]})retained in the blocked port information memory unit 20[1]. Therefore,rewriting of the blocked port information occurs in the blocked portinformation memory unit 20[1].

Furthermore, the blocked port information ({SWd}, {Pr[1]}) contained inthe R-APS (SF) frame is different also from blocked port informationretained in the blocked port information memory unit 20[2] (blank inthis case). In this manner, when rewriting of the blocked portinformation occurs and rewritten blocked port information is differentfrom blocked port information retained in the other blocked portinformation memory unit, the relay device SWc flushes the address table(FDB).

Also, as indicated by step S105, when the relay device SWa serving as anowner node receives the R-APS (SF) frame from the relay device SWe, therelay device SWa releases the block state BK of the ring port Pr[1](namely, changes the ring port Pr[1] to an open state) and flushes theaddress table (FDB). At this time, since the relay device SWa receivesthe R-APS (SF) frame in a period when the ring port Pr[1] is in theblock state BK, the relay device SWa does not relay the R-APS (SF) frameto the ring port Pr[1].

In the same manner, as indicated by step S105, when the relay device SWbserving as a neighbor node receives the R-APS (SF) frame from the relaydevice SWd, the relay device SWb also releases the block state BK of thering port Pr[2] and flushes the address table (FDB). At this time, sincethe relay device SWb receives the R-APS (SF) frame in a period when thering port Pr[2] is in the block state BK, the relay device SWb does notrelay the R-APS (SF) frame to the ring port Pr[2].

Subsequently, as indicated by step S106, the relay devices SWd and SWeboth transmit second R-APS (SF) frames. For example, based on ITU-TG.8032, the R-APS (SF) frame is transmitted three times every 3.3 ms,and is thereafter transmitted every 5 s. In this case, the second R-APS(SF) frame is transmitted after 3.3 ms of the transmission of the firstR-APS (SF) frame.

The second R-APS (SF) frame transmitted by the relay device SWd passesthrough the ring port Pr[2] of the relay device SWb that is releasedfrom the block state BK at step S105 mentioned above. In the samemanner, the second R-APS (SF) frame transmitted by the relay device SWealso passes through the ring port Pr[1] of the relay device SWa that isreleased from the block state BK at step S105 mentioned above.

As a result, as indicated by step S107, for example, the relay deviceSWc receives the R-APS (SF) frame containing blocked port information({SWe}, {Pr[2]}) that is transmitted from the relay device SWe. In thiscase, rewriting of the blocked port information occurs in the blockedport information memory unit 20[2] of the relay device SWc, and therewritten blocked port information is different from the blocked portinformation retained in the blocked port information memory unit 20[1].Thus, the relay device SWc flushes the address table (FDB).

Furthermore, though details thereof are omitted, the other relay devicesSWa, SWb, SWd, and SWe also execute the flushing of the address table(FDB) in the same manner in response to the rewriting of the blockedport information. After that, the R-APS (SF) frame is transmitted atregular intervals by the relay devices SWd and SWe, but a steady stateis reached because rewriting of the blocked port information does notoccur.

FIG. 4 is a diagram illustrating a frame transfer path after pathswitching of the ring network is performed by the operation of FIG. 3.When the operation of FIG. 3 has been executed and the steady state hasbeen reached, a communication path 25 via the relay devices SWa, SWb andSWc is formed between the relay device SWe and the relay device SWd asillustrated in FIG. 4. The frame transfer between the user networks 11 ato 11 e is performed on this communication path 25.

<<Problem of Relay System (Premise)>>

As described above with reference to FIG. 3, each relay device (forexample, SWc) usually starts the flushing (deletion) of the addresstable (FDB) in response to the first R-APS (SF) frame (step S104), andstarts the flushing again in response to the second R-APS (SF) frame(step S107). The interval between the first flushing and the secondflushing is, for example, 3.3 ms, but the flushing of the address table(FDB) sometimes takes a flush time (Tf) of 10 ms or longer.

In such a case, for example, the flushing of the address table (FDB) isstarted, and after 3.3 ms of the start of the flushing, namely, duringthe execution of the flushing, the flushing is started again (in otherwords, the flushing is restarted all over again). As a result, the timeof “3.3 ms+flush time (Tf)” is required from the reception of the firstR-APS (SF) frame to the actual completion of the flushing of the addresstable (FDB).

Furthermore, in the example of FIG. 3, the second R-APS (SF) frame atstep S106 passes through the ring port released from the block state BKat step S105. However, it actually takes a time longer than 3.3 ms torelease the block state BK in some cases. In this case, the second R-APS(SF) frame is blocked in the same manner as the first R-APS (SF) frame,and the frame which passes through the ring port released from the blockstate BK is a third R-APS (SF) frame in some cases. Consequently, a timeof 3.3 ms is further added for the completion of the flushing of theaddress table (FDB).

<<Outline of Relay Device (Present Embodiment)>>

FIG. 5 is an explanatory diagram schematically illustrating an operationexample of the principle part of the relay device according to the firstembodiment of the present invention. FIG. 5 illustrates an operationexample of at least any one of the relay devices in the relay system ofFIGS. 1 and 3. In FIG. 5, although the operation of the relay device SWcof FIG. 3 is described here as a typical example, the same operation canbe applied also to the other relay devices SWa, SWb, SWd, and SWe.

At time t1 in FIG. 5, the relay device SWc receives a first addresstable (FDB) flushing (deletion) command through the ring network.Specifically, the relay device SWc receives the flushing command via thecontrol frame (R-APS (SF) frame) from the relay device SWd indicated bystep S103 of FIG. 3. In this case, the subject of the first flushingcommand is assumed to be an entry having a VLAN (Virtual LAN) identifier(VID)=1 in the address table (FDB).

Subsequently, at time t2, the relay device SWc prohibits a learningprocess to the address table (FDB). At this time, the relay device SWcmay prohibit a learning process to an entry having the VID=1, which isthe subject of the first flushing command. Thereafter, at time t3, therelay device SWc starts flushing (deletion) of the address table (FDB).

Subsequently, in a period before the completion of the flushing of theaddress table (FDB), the relay device SWc receives a second flushingcommand at time t4 through the ring network. Specifically, the relaydevice SWc receives the flushing command via the control frame (R-APS(SF) frame) from the relay device SWe indicated by step S106 of FIG. 3.The subject of the second flushing command is the same entry having theVID=1 in the address table (FDB) as the subject of the first flushingcommand.

When receiving the second flushing command, the relay device SWccontinues to execute the flushing of the address table (FDB) started attime t3, as indicated at time t5. Namely, the relay device SWc does notstart the flushing of the address table (FDB) again (in other words,does not restart the flushing all over again). Also, though notillustrated, the relay device SWc continues to execute the flushing ofthe address table (FDB) in the same manner also when receiving a N-th (Nis an integer of 2 or more) flushing command as well as the secondflushing command in the period before the completion of the flushing ofthe address table (FDB).

Thereafter, the relay device SWc completes the flushing of the addresstable (FDB) at time t6 and then permits the learning process to theaddress table (FDB) at time t7. As described above, in FIG. 5, a periodTc between time t1 and time t4 is, for example, 3.3 ms and a period Tfbetween time t3 and time t6 (that is, a flush time of the address table(FDB)) is, for example, 10 ms or longer.

As described above, by use of the operation illustrated in FIG. 5, thetime from reception of the first flushing (deletion) command of theaddress table (FDB) through the ring network to the actual completion ofthe flushing (deletion) of the address table (FDB) can be shortened.Namely, as described above, if the flushing is started again in responseto the second flushing command, for example, the flush time Tf staringfrom time t5 is required. Meanwhile, in the case of adopting the methodof FIG. 5, the flush time Tf staring from time t3 suffices for thecompletion of the flushing. As a result, the high-speed path switchingon the ring network 10 can be realized. In addition, since it is notnecessary to consecutively repeat the flushing of the address table(FDB) several times in the relay device, the processing load and powerconsumption can be reduced.

Here, the reason why it is not necessary to start the flushing again attime t5 is that the learning process to the address table (FDB) isprohibited at time t2. Thus, since no new entry is learned to theaddress table (FDB) in a period between time t3 and time t5, it is alsonot necessary to start the flushing again. Although the learning processto the address table (FDB) is prohibited in a period between time t2 andtime t7 in this example, actually, it is desirable to prohibit also aretrieval process to the address table (FDB) in order to prevent theframe from being relayed to a wrong path.

Also, the relay device can carry out the flushing of the address table(FDB) for an entry having a predetermined VLAN identifier (VID) andentries having the ring ports (first and second ports) Pr[1] and Pr[2].In this case, if the second flushing command at time t4 is the flushingcommand for a VLAN identifier (VID) different from the VLAN identifier(VID) that is the subject of the first flushing command, the relaydevice newly starts the flushing of the address table (FDB) for the VLANidentifier (VID) that is the subject of the second flushing command attime t5.

<<Configuration of Relay Device (Present Embodiment)>>

FIG. 6 is a block diagram illustrating a configuration example of therelay device of FIG. 5. FIG. 7 is a schematic diagram illustrating aconfiguration example of the address table of FIG. 6. The relay deviceSW illustrated in FIG. 6 includes the ring ports (first and secondports) Pr[1] and Pr[2], the plurality of user ports Pu[1] to Pu[m], andvarious processing units. As illustrated in FIG. 1, the ring ports(first and second ports) Pr[1] and Pr[2] are connected to the ringnetwork 10 via a communication line (for example, Ethernet line) 27. Theplurality of user ports Pu[1] to Pu[m] are connected to predetermineduser networks (any of user networks 11 a to 11 e). Hereinafter, theprocessing units will be described.

When an interface unit 30 receives a frame at any of the plurality ofports (ring ports Pr[1] and Pr[2] and user ports Pu[1] to Pu[m]), itadds an identifier of a port which has received the frame (referred toas reception port identifier) to the frame and transmits the frame to aframe processing unit 31 or a processor unit CPU. Also, the interfaceunit 30 transmits a frame from the frame processing unit 31 or theprocessor unit CPU to any of the plurality of ports based on adestination port identifier described later.

The address table FDB retains the correspondence relation among MAC(Media Access Control) addresses, VLAN identifiers (VID), and theplurality of ports. Specifically, as illustrated in FIG. 7, the addresstable FDB retains the correspondence relation among the MAC address, theVID, and the port identifier (ID) for each entry. In the example of FIG.7, the correspondence relation among a MAC address MA1, a VID=1, and aring port identifier {Pr[1]} is retained at an entry number=1, and thecorrespondence relation among a MAC address MA2, the VID=1, and a ringport identifier {Pr[2]} is retained at an entry number=2.

The frame processing unit 31 is provided with an FDB processing unit 34,a VID filter 35, and an OAM processing unit 36. The FDB processing unit(address table processing unit) 34 carries out a process to the addresstable FDB. Specifically, when receiving a frame (for example, userframe) at any of the plurality of ports, the FDB processing unit 34carries out a learning process and a retrieval process to the addresstable FDB.

In the learning process, the FDB processing unit 34 learns a source MACaddress contained in the received user frame to the address table FDB inassociation with predetermined VID and reception port identifier addedby the interface unit 30. The predetermined VID is determined by aso-called tag VLAN, port VLAN, and others. In the retrieval process, theFDB processing unit 34 retrieves the address table FDB with using adestination MAC address contained in the received user frame and a VIDcorresponding to the destination MAC address as retrieval keys. The FDBprocessing unit 34 adds a port identifier obtained by the retrievalresult (referred to as destination port identifier) to the user frame,and transmits the user frame to the interface unit 30.

The VID filter 35 determines whether or not a frame may be relayed inaccordance with the VID. For example, the block state BK illustrated inFIG. 1 and others is realized by this VID filter 35. The OAM processingunit 36 has the monitoring points (MEP) illustrated in FIG. 2, andmonitors continuity based on the Ethernet OAM. The OAM processing unit36 has a R-APS processing unit 37.

The R-APS processing unit 37 performs the process of R-APS frames basedon ITU-T G.8032. Specifically, the R-APS processing unit 37discriminates a R-APS frame from among received frames and notifiesvarious control information contained in the R-APS frame to an ERPcontrol unit 38 described later. Contrary to that, the R-APS processingunit 37 generates a R-APS frame containing various control informationnotified from the ERP control unit 38, and transmits the R-APS framefrom a predetermined ring port.

The processor unit CPU performs the various communication protocolprocesses, for which complicated process is required, in cooperationwith the frame processing unit 31 or manages the overall relay devicebased on software (firmware) stored in a memory unit 33. The processorunit CPU is provided with an ERP control unit (ring control unit) 38configured by executing firmware.

The ERP control unit (ring control unit) 38 controls the ring networkbased on the ring protocol specified by ITU-T G.8032. Specifically, theERP control unit 38 controls the ring network by transmitting andreceiving a control frame (that is, R-ARS frame) through the ring port(first port Pr[1] or second port Pr[2]) via the R-APS processing unit37. Then, the ERP control unit 38 receives a flushing (deletion) commandof the address table FDB described in FIG. 5 via the control frame.

Here, the FDB processing unit 34 performs various processes to theaddress table FDB illustrated in FIG. 5 when the ERP control unit 38receives a flushing command, in addition to the learning process andretrieval process described above. Specifically, when a first flushingcommand is received, the FDB processing unit 34 prohibits the learningprocess of correspondence relation to the address table FDB and thenstarts flushing (deletion) of the address table FDB. Also, when a N-th(N is an integer of 2 or more) flushing command is received in a periodbefore the completion of the flushing of the address table (FDB), theFDB processing unit 34 continues to execute the flushing of the addresstable FDB.

<<Ring Protocol Operation of Relay Device (Present Embodiment)>>

FIG. 8 is an explanatory diagram schematically illustrating an operationexample around the ERP processing unit and the OAM processing unit inthe relay device of FIG. 6. In FIG. 8, the monitoring points MEP1 andMEP2 in the OAM processing unit 36 generate a CCM frame at regularintervals and transmit the CCM frame from the ring ports Pr[1] and Pr[2]via the interface unit 30, respectively. Also, the monitoring pointsMEP1 and MEP2 discriminate the CCM frame from among the frames receivedat the ring ports Pr[1] and Pr[2] and transmitted via the interface unit30, respectively. The CCM frame is discriminated based on, for example,a destination MAC address of the frame and various identifiers in theframe.

The monitoring points MEP1 and MEP2 determine the presence or absence ofcontinuity of the link connected to the ring ports Pr[1] and Pr[2] bytransmitting and receiving the CCM frames at regular intervals,respectively. The determination result of the presence or absence ofcontinuity (that is, presence or absence of recognition of the LOC stateor RDI state) is notified to the ERP control unit 38. For example, whenthe absence of continuity is notified, the ERP control unit 38 performsthe setting of a predetermined ring port, VID and others in the VIDfilter 35, thereby controlling the predetermined ring port to the blockstate BK as indicated by, for example, step S102 of FIG. 3.

The R-APS processing unit 37 transmits and receives a R-APS frame viathe monitoring points MEP1 and MEP2. As described above, the R-APS frameis a kind of a control frame based on Ethernet OAM. When the R-APSprocessing unit 37 transmits the R-APS frame, the ERP control unit 38inserts predetermined control information (R-APS information) in theR-APS frame. The predetermined control information (R-APS information)means a variety of information specified by ITU-T G.8032 typified by SF,NR, RB and others as described in FIG. 3.

Also, when the R-APS processing unit 37 receives the R-APS frame, theERP control unit 38 extracts the predetermined control information(R-APS information) contained in the R-APS frame. Then, the ERP controlunit 38 performs a predetermined control operation in accordance withthe extracted control information. The predetermined control operationmeans various operations specified by ITU-T G.8032 typified by variouscontrol operations described in FIG. 3.

Specifically, the predetermined control operations include, for example,control of the block state BK for a ring port (for example, step S105 ofFIG. 3) and control of relaying the R-APS frame between ring ports. Thepredetermined control operations further include comparison and updateof blocked port information in the blocked port information memory units20[1] and 20[2] and transmission of a flushing (deletion) executionrequest of the address table FDB in accordance with the comparisonresult illustrated in FIG. 3. The blocked port information memory units20[1] and 20[2] are disposed in, for example, the memory unit 33 asillustrated in FIG. 8.

<<Flushing (Deletion) Operation of Address Table>>

FIG. 9 is a flowchart illustrating an example of process contentsperformed by the FDB processing unit of FIGS. 6 and 8. As a premise, itis assumed that the ERP control unit (ring control unit) 38 of FIG. 8transmits a flushing (deletion) execution request of the address tableFDB to the FDB processing unit 34 every time when receiving a flushingcommand of the address table FDB via the ring network. In FIG. 9, theFDB processing unit 34 determines whether it has received a firstflushing execution request [1] for a predetermined VID from the ERPcontrol unit 38 (step S101).

When having received the flushing execution request [1], the FDBprocessing unit 34 prohibits a learning process and a retrieval processto the address table FDB (step S102). At this time, the FDB processingunit 34 may prohibit the learning process and the retrieval process fora predetermined VID, which is the subject of the first flushingexecution request [1]. Thereafter, the FDB processing unit 34 startsflushing (deletion) of the address table FDB (step S103).

In this case, when the VID=1 is the subject of the first flushingexecution request [1] at step S101, the FDB processing unit 34determines the entry number=1 and entry number=2 (that is, entriesincluding the VID=1 and ring port) illustrated in FIG. 7 as the subjectof the flushing process. In other words, the FDB processing unit 34 doesnot determine an entry including a user port (entry number=i) or anentry including a different VID (entry number=j and entry number=k) asthe subject of the flushing process.

Subsequently, the FDB processing unit 34 then determines whether theflushing of the address table FDB is completed (step S104). When havingcompleted the flushing, the FDB processing unit 34 permits the learningprocess and retrieval process to the address table FDB (step S105) andends the series of steps.

Meanwhile, when the FDB processing unit 34 does not complete theflushing yet (that is, the flushing is being executed) and receives asecond flushing execution request [2] for the same VID that is thesubject of the first flushing execution request [1] from the ERP controlunit 38 (step S106), the FDB processing unit 34 discards the secondflushing execution request [2] (step S107). In other words, whenreceiving a N-th (N is an integer of 2 or more) flushing executionrequest corresponding to a N-th flushing command from the ERP controlunit 38, the FDB processing unit 34 discards the N-th flushing executionrequest.

As described above, by using the relay system and the relay device ofthe first embodiment, typically, the high-speed path switching on thering network can be realized. This effect is particularly advantageouswhen the ring protocol specified by ITU-T G.8032 is adopted. Note thatthe relay device SW illustrated in FIG. 6 may be a box-type relay deviceor chassis-type relay device.

Second Embodiment Flushing (Deletion) Operation of Address Table(Modification Example)

FIG. 10 is a flowchart illustrating an example of the process contentsperformed by the ERP control unit of FIGS. 6 and 8 in a relay deviceaccording to the second embodiment of the present invention. In theflowchart of FIG. 9 of the first embodiment, the FDB processing unit 34performs the operation executed at time t5 of FIG. 5. However, asillustrated in FIG. 10, the operation at time t5 can be performed alsoby the ERP control unit 38.

In FIG. 10, the ERP control unit 38 determines whether it has received afirst flushing (deletion) command of address table FDB for apredetermined VID via the ring network (step S201). When having receivedthe flushing command, the ERP control unit 38 transmits a flushing(deletion) execution request of the address table FDB to the FDBprocessing unit 34 (step S202). In response to the request, the FDBprocessing unit 34 performs the operations at time t2 and time t3illustrated in FIG. 5.

Thereafter, the ERP control unit 38 determines whether it has received aflushing completion notification from the FDB processing unit 34 (stepS203). When the ERP control unit 38 does not receive the flushingcompletion notification yet (that is, the FDB processing unit 34 isstill executing the flushing) and receives a second flushing command forthe same VID that is the subject of the first flushing command via thering network (step S204), the ERP control unit 38 transmits no flushingexecution request (step S205). As a result, the FDB processing unit 34performs the operation at time 5 illustrated in FIG. 5.

As described above, also by using the relay device of the secondembodiment, the same effect as the relay device of the first embodimentcan be obtained. From the viewpoint of realizing the operation specifiedby ITU-T G.8032, however, it is sometimes desirable that the ERP controlunit 38 is configured to prompt the execution of the flushing command(that is, transmit a flushing execution request) every time whenreceiving the flushing command via the ring network. From thisviewpoint, the method in FIG. 9 of the first embodiment is morepreferable.

In the foregoing, the invention made by the inventor of the presentinvention has been concretely described based on the embodiments.However, it is needless to say that the present invention is not limitedto the foregoing embodiments and various modifications and alterationscan be made within the scope of the present invention. For example, theembodiments above have been described in detail so as to make thepresent invention easily understood, and the present invention is notlimited to the embodiment having all of the described constituentelements. Also, a part of the configuration of one embodiment may bereplaced with the configuration of another embodiment, and theconfiguration of one embodiment may be added to the configuration ofanother embodiment. Furthermore, another configuration may be added to apart of the configuration of each embodiment, and a part of theconfiguration of each embodiment may be eliminated or replaced withanother configuration.

For example, although the case where a neighbor node is set in a ringnetwork is taken as an example in the description above, the method ofthe present embodiment can be similarly applied also to the case where aneighbor node is not set and only an owner node is set. Furthermore, theERP control unit 38 does not necessarily need to be configured by theprocessor unit CPU, and may be configured by dedicated hardwaredepending on the case.

Also, although the operation in the occurrence of a fault (SF) is takenas an example in the description above, the same problem may arise atthe neighbor node in the recovery from a fault as described in thePatent Document 1. Briefly describing, when the neighbor node (SWb ofFIG. 3) receives a first R-APS (NR, RB) frame from the owner node inaccordance with the recovery from a fault, the neighbor node controls apredetermined ring port (Pr[2]) to the block state BK and startsflushing the address table, thereby deleting information retained in theblocked port information memory unit. Therefore, when the neighbor nodereceives a second R-APS (NR, RB) frame, the blocked port informationmemory unit is updated, and the flushing of the address table needs tobe started again in some cases. Even in such a case, by applying themethod of the embodiments described above, the start of the second andsubsequent flushing processes can be avoided.

What is claimed is:
 1. A relay system including a plurality of relay devices constituting a ring network, at least one of the plurality of relay devices comprising: a plurality of ports including a first port and a second port connected to the ring network; an address table processor that performs a process on an address table retaining a correspondence relation among a MAC address, a VLAN identifier, and the plurality of ports; and an Ethernet Ring Protection controller that controls the ring network by transmitting and receiving a control frame through the first port or the second port and receives deletion commands to delete the address table via the control frame, wherein, when a first deletion command of the deletion commands is received, the address table processor prohibits a learning process of the correspondence relation retained in the address table and then starts deleting the address table, and when N is an integer of 2 or more and a N-th deletion command of the deletion commands is received in a period before completion of the deletion of the address table, the address table processor continues to execute the deletion of the address table.
 2. The relay system according to claim 1, wherein the Ethernet Ring Protection controller controls the ring network based on a ring protocol specified by ITU-T G.8032, and receives the deletion command to delete the address table via a R-APS (SF) frame.
 3. The relay system according to claim 1, wherein, when the first deletion command is received, the address table processor prohibits also a retrieval process of the correspondence relation in addition to the learning process of the correspondence relation retained in the address table.
 4. The relay system according to claim 1, wherein, when the N-th deletion command is received and the VLAN identifier which is a subject of the N-th deletion command is the same as the VLAN identifier which is a subject of the first deletion command, the address table processor continues to execute the deletion of the address table.
 5. The relay system according to claim 1, wherein, every time when receiving the deletion command, the Ethernet Ring Protection controller transmits a deletion execution request for executing deletion of the address table to the address table processor, and when receiving a N-th deletion execution request corresponding to the N-th deletion command from the Ethernet Ring Protection controller, the address table processor discards the N-th deletion execution request.
 6. A relay device constituting a ring network, comprising: a plurality of ports including a first port and a second port connected to the ring network; an address table which processor that performs a process on an address table retaining a correspondence relation among a MAC address, a VLAN identifier, and the plurality of ports; and an Ethernet Ring Protection controller that controls the ring network by transmitting and receiving a control frame through the first port or the second port and receives deletion commands to delete the address table via the control frame, wherein, when a first deletion command of the deletion commands is received, the address table processor prohibits a learning process of the correspondence relation retained in the address table and then starts deleting the address table, and when N is an integer of 2 or more and an N-th deletion command of the deletion commands is received in a period before completion of the deletion of the address table, the address table processor continues to execute the deletion of the address table.
 7. The relay device according to claim 6, wherein the Ethernet Ring Protection controller controls the ring network based on a ring protocol specified by ITU-T G.8032, and receives the deletion command to delete the address table via a R-APS (SF) frame.
 8. The relay device according to claim 6, wherein, when the first deletion command is received, the address table processor prohibits also a retrieval process of the correspondence relation in addition to the learning process of the correspondence relation retained in the address table.
 9. The relay device according to claim 6, wherein, when the N-th deletion command is received and the VLAN identifier which is a subject of the N-th deletion command is the same as the VLAN identifier which is a subject of the first deletion command, the address table processor continues to execute the deletion of the address table.
 10. The relay device according to claim 6, wherein, every time when receiving the deletion command, the Ethernet Ring Protection controller transmits a deletion execution request for executing deletion of the address table to the address table processor, and when receiving a N-th deletion execution request corresponding to the N-th deletion command from the Ethernet Ring Protection controller, the address table processor discards the N-th deletion execution request. 